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SubjectRe: How to efficiently handle DMA and cache on ARMv7 ? (was "Is get_user_pages() enough to prevent pages from being swapped out ?")
Laurent Pinchart a écrit :
> On Thursday 06 August 2009 20:46:14 David Xiao wrote:
>
> Think about the simple following use case. An application wants to display
> video it acquires from the device to the screen using Xv. The video buffer is
> allocated by Xv. Using the v4l2 user pointer streaming method, the device can
> DMA directly to the Xv buffer. Using driver-allocated buffers, a memcpy() is
> required between the v4l2 buffer and the Xv buffer.
>
v4l2 got an API (overlay IRRC) that allow drivers to write directly in
framebuffer memory.
BTW Xv buffer is not always in video memory and the X driver can do a
memcpy.


Matthieu
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